The European Commission proposed tightening controls on cash and precious metals transfers from outside the EU on Wednesday, in a bid to shut down one route for funding of militant attacks on the continent.

The move follows Monday’s attack on a Christmas market in Berlin, where 12 people were killed as a truck ploughed into a crowd. It is part of an EU “action plan against terrorist financing” unveiled after the bombings and shootings in Paris in November 2015.

Under the new proposals, customs officials in European Union states can step up checks on cash and prepaid payment cards sent by post or in freight shipments.

Authorities will also be able to seize cash or precious metals carried by suspect individuals entering the EU.